| In recent years,with the rapid development of our economy and the continuous improvement of the industrial system,the demand of users for electricity is also growing.And with all kinds of precision instruments connected to the power grid,the power quality of the power grid is also improving.Therefore,accurate monitoring and evaluation of various indicators of power quality is of great significance to improve the operation safety of electrical equipment,enhance the overall benefits of economic development,and ensure the level of people's production and life.In order to take reasonable measures to improve power quality,first of all,it is necessary to carry out accurate detection and reasonable and effective evaluation of power quality.Based on this,the following research work has been done in this paper:Firstly,the basic definition and background of power quality are put forward,as well as the hazards,detection methods and national standards of frequency deviation,voltage deviation,harmonic,three-phase unbalance,voltage fluctuation and flicker,voltage sag and three-phase unbalance of seven power quality indicators.Based on these,the power quality evaluation grade and power quality evaluation system are established.Secondly,the LabVIEW program based on virtual instrument software development platform is designed.The software of power quality monitoring system is elaborately designed,including the overall design scheme and design flow chart,including basic electrical parameters,voltage fluctuation and flicker,three-phase unbalance and power harmonic measurement methods and software design procedures.Finally,the power quality index weighting method and evaluation method model are established.Aiming at the problems existing in subjective and objective empowerment methods,a combined empowerment method is proposed.The method of combining analytic hierarchy process with entropy weight method is used to determine the weight of power quality index,which overcomes the shortcomings of over-reliance on experience and preference in subjective weighting method and over-use of mathematical information in objective weighting method,thus fully absorbs the advantages of both methods and realizes the complementary advantages of the two methods.A comprehensive evaluation model of power quality is presented based on the fuzzy Borda ranking method.Extension comprehensive evaluation algorithm,TOPSIS and fuzzy comprehensive evaluation algorithm are used to evaluate the single power quality.The combined results are calculated by using the fuzzy Borda method.The actual monitoring data of an enterprise are used to verify the validity of the model. |
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